1. Field of the Invention
This invention relates to a semiconductor laser device.
2. Description of the Prior Art
This invention provides a novel structure which permits the direct modulation of a semiconductor laser device. Also, this invention provides a novel structure which permits the mode control of a semiconductor laser device.
Since semiconductor laser devices are small in size and high in efficiency and are capable of fast modulation, the optical communication and other various applications such as data buses and computer links are considered.
In order to modulate the semiconductor laser device, current pulses of 30-200 mA are usually impressed on the device. However, when the modulation signal becomes a high speed on the order of 1-2 Gbits/sec, it is difficult to produce such great current pulses and directly modulate the laser device by means of a conventional silicon transistor.
In recent years, therefore, attempts to employ a GaAs-based material capable of faster modulation and to integrate a laser device and a field-effect transistor (hereinbelow, abbreviated to "FET") have been made. An example is described in a paper by I. Ury et al. contained in Appl. Phys. Lett. 34(7), April 1, 1979, pp. 430-431. Such examples, however, merely integrate the semiconductor laser and the FET on a single substrate.